Poly (omega-amino carboxylic acid) compositions stabilized with a copper salt and iodoform

ABSTRACT

POLYAMIDE COMPOSITIONS SUITABLE FOR TEXTILE FILAMENT, FIBERS AND YARNS ARE STABILIZED AGAINST DEGRADATION BY INCORPORATING COPPER AND IODINE-CONTAINING COMPOUNDS.

United States Patent US. Cl. 26045.75 4 Claims ABSTRACT OF THE DISCLOSURE Polyamide compositions suitable for textile filament, fibers and yarns are stabilized against degradation by incorporating copper and iodine-containing compounds.

This invention relates to synthetic poly(w-amino carboxylic acid) compositions which are stabilized against degradation under the influence of heat and light, and to articles made from such compositions, especially textile filaments, fibres and yarns.

It is known that synthetic polyamides suffer a deterioration of their mechanical properties under the influence of heat and light. When such polyamides are exposed for some time to higher temperatures or to radiation, especially radiation containing ultra-violet rays, they usually become brittle, and their tensile strength decreases considerably. Parallel to this mechanical degradation, the polyamides show a decrease of their viscosity indicating a reduction of their average molecular weight. Since shaped articles, especially textile filaments and yarns, made from polyamides are widely used because of their excellent mechanical properties, the heatand light-sensitivity of such articles is a great disadvantage, and many efforts have been made to prepare synthetic polyamides which retain their strength after exposure to higher temperatures or to light.

A great variety of substances has been proposed as stabilizers for polyamides, and especially copper and combinations of copper with other chemicals have been recommended. Thus, German Pat. glo. 883,644 describes the use of copper, copper oxide, and copper salts; British Pat. No. 652,947 mentions copper salts of fatty acids or beta-diketones; and United States Pat. No. 2,705,227 proposes a combination of copper, alkali halides, especially bromides and iodides, and alkali phosphates. Swiss Patent No. 364,116 comments however that copper salts and inorganic halides are not compatible with each other as they incline to form deposits, and therefore suggests the use of a mixture of copper salts with bromides or iodides of organic bases. British Patent No. 864,701 uses a combination of copper salts, halides of organic bases and phosphorus oxy-acids, and British Pat. No. 908,647 proposes as a stabilizer cuprous iodide with the optional addition of a little potassium iodide which is said to help in maintaining the valency state of the cuprous ion. Another solution is suggested by British Pat. No. 922,706 which uses copper salts of halogen-substituted organic acids or complex salts of copper halides with amines.

A considerable disadvantage of the use of copper salts as stabilizers is that they may produce a yellow to red discoloration of the polyamide, which is especially unpleasant when it is desired to obtain colorless or white textile fibers.. Other difliculties are described in detail by British Patent No. 924,629; there is often a tendency for the copper to separate from the polyamide and to form a deposit which may block the spinning filters and interrupt the spinning process. Another consequence of such precipitation of copper is a reduction of the copper con- 3,629,188 Patented Dec. 21, 1971 tent of the polyamide whereby the stabilizing effect is diminished. It is known that discoloration of polyamides and precipitation of copper can be suppressed by the addition of iodides, but, according to British Pat. No. 924,629, the iodides are apparently the cause of another trouble, namely the formation of molten polyamide blobs at the spinneret face which again interferes with the spinning process. As a solution of these difiiculties, this British patent proposes to use as stabilizers copper and elementary iodine, but the handling of larger quantities of elementary iodine is somewhat troublesome and requires special safety precautions.

British Patent No. 924,629 also prescribes that at least one, and preferably, five atoms of iodine should be present for each atom of copper, and it appears that similar ratios are required when iodine containing salts or acids are employed in accordance with the above-mentioned specifications. However, the use of such substances produces another diificulty. The iodine containing salts or acids are electrolytes, and, when used in the quantities prescribed, have the unpleasant effect of coagulating pigments contained in the polyamide and of preventing their proper dispersion. This is especially troublesome when, for example, delustered polyamide fibers are to be produced using titanium dioxide as a pigment.

The various difficulties in using copper and iodides increase, when it is desired to prepare polyamide compositions which contain stabilizers in concentrated form. Such concentrates are required in continuous polycondensation processes, where it is usual to mix a major proportion of a basic unstabilized polyamide with a small quantity of the required type of concentrate containing the desired additives, such as stabilizers, pigments, dyes, optical brighteners, etc. The concentrate and the basic polyamide are usually mixed in proportions between 1 to 10 and 1 to 20, but sometimes proportions up to 1 to are required. It follows that the concentrate must contain 10, 20 or 100 times the quantity of additives that are desired in the final product. When copper salts alone are used as stabilizers, such procedure always results in final products having an unpleasant pink to violet discoloration, and, if such discoloration is suppressed by the addition of a sufiicient quantity of iodides, e.g. of potassium iodide, it is not possible to disperse titanium dioxide in the polyamide and to obtain delustered products.

It is an object of this invention to provide heatand light-stabilized poly(w-amino carboxylic acid) compositions which are not discolored, which can be pigmented, and which, during manufacture, do not produce undesired deposits in polycondensation or melt-spinning installations.

Another object is to provide pigmentable poly(w-amino carboxylic acid) compositions containing stabilizers in a concentrated form which, when mixed with a major proportion of unstabilized poly(w-amino carboxylic acid), yield undiscolored heatand light-stabilized poly(w-amino carboxylic acid) compositions.

These and other objects are accomplished by the present invention which provides poly(w-amino carboxylic acid) compositions stabilized against degradation by heat and light by the incorporation with the poly(w-amino carboxylic acid) during manufacture of copper or a copper compound and an iodine-substituted aliphatic or alicyclic hydrocarbon.

The copper may be derived from any source. Thus, both elementary copper, and any suitable inorganic or organic copper compound can be used, for example, oxides, chlorides, bromides, iodides, borates, phosphates, acetates, oxalates, butyrates, lactates, stearates, benzoates, salicylates, phthalates, or naphthenates of copper. The copper may be in the cuprous or cupric state.

The iodine-substituted hydrocarbon may be of the aliphatic, or alicyclic type, and may be a monovalent or a polyvalent iodine compound, and may also contain, in addition to iodine, other elements, e.g. halogens other than iodine, for examples, 1,2 diiodo-ethane, 1,1,1-triiodoethane, 1,6-diiodo-hexane. Iodo-cyclopentane is very satisfactory, but the preferred substance is iodoform which is easily available and safe to handle.

To make polymers for direct use, the stabilizers are preferably employed in quantities corresponding to between 20 and 100 parts by weight of copper and between 50 and 250 parts by weight of iodine, per million parts of poly(w-amin carboxylic acid). For concentrates however which are to be mixed with a basic unstabilized polyamide, the quantities of stabilizers used may correspond to between 100 and 5,000 parts by weight of copper and between 250 and 20,000 parts by weight of iodine, per million parts of poly(w-arnino carboxylic acid), according to the intended mixing proportion.

If it is desired to prepare pigmented concentrates, for example by using titanium dioxide as delustering agent, it is recommended to select as the copper compound a stabilizer which, in aqueous solution, dissociates very little or not at all, to avoid coagulation of the pigment.

When making polymers both for direct use and for concentrates, the stabilizers should be employed in such quantities that there is at least one atom of iodine present for one atom of copper. If desired, other known stabilizers, for example phenolic antioxidants or phosphorus oxyacids, can be added.

Poly (w-amino carboxylic acid) compositions for direct use made according to the invention are colorless or, if pigmented, of a pure white. They possess an excellent protection against mechanical degradation by heat and light which considerably surpasses the protection afforded by the use of copper alone. When these poly(w-amino car boxylic acid) compositions are manufactured and processed, there is no precipitation of copper in polycondensation installations or spinning filters and no formation of molten polyamide blobs at the spinnerets. Iodine-substituted hydrocarbons alone have no stabilizing effect.

The stabilized concentrates described above which contain to 100 times the quantities of stabilizers incorporated in polymers for direct use, are usually colored, but the color disappears when the concentrates are mixed with the required quantity of unstabilized basic polymer, and fibers and other articles formed from the mixture are colorless or white, respectively. Also there is no precipitation of copper when the concentrates are prepared, and they can be delustered by the addition of titanium dioxide without difficulty.

As already indicated, the stabilizers are incorporated into the poly(w-amino carboxylic acid) during its manufacture, preferably before or during polycondensation. The conditions for the polycondensation are conventional. For example, caprolactam is melted at about 90 C. and about 1 percent by weight of water is added under stirring containing the copper and iodine compound and other additions, as e.g. titanium dioxide. When making polymers for direct use, 0.1 percent by weight of benzoic acid are also added as chain terminator, while such addition is not necessary when making polymer concentrates. The mixture is heated under nitrogen during 2 hours at 250 C. in an autoclave. Then the pressure is released within 10 minutes, and polymerization continued under nitrogen during 4 hours at the same temperature. The polymer is extruded as usual, washed during 24 hours with water at C. to extract the monomers, and finally dried during 3 days at 70 C. under reduced pressure.

The invention is illustrated by the following examples in which the incorporation of the stabilizers and the polycondensation schedule was as described above. The color of spun yarns is given according to visual observation. The reduced viscosity (1 is calculated according to the formula:

( ln 1; rel

7I)O.2-W wherein the relative viscosity 7 rel is determined in a solution containing 0.2 g. of polycaprolactam fiber in ml. of 94% sulfuric acid at a temperature of 20 C. The tensile strength, expressed in grams per denier, is measured as usual, and the irradiation test is carried out with an Atlas Fadeometer, Type FDA-R made by Atlas Electric Devices 00., Chicago, 111., USA, according to a method described in the Technical Manual of the American Association of Texile Chemists and Colorists, published by Howes Publishing Co., New York, 1957. The examples describe stabilization of polycaprolactam, at present the most important poly(w-amino carboxylic acid), but the invention can equally be applied to other poly(w-amino carboxylic acids), for example, to poly(w-amino undecanoic acid), poly(w-amino enanthic acid), poly(w-amino caprylic acid), poly(w-amino lauric acid), and poly(wamino tridecylic acid).

EXAMPLE 1 Five polycaprolactam compositions are prepared as described above, each made from 5 kg. of caprolactam, but with different additions, the term parts Cu meaning parts by weight of copper, and the term parts J meaning parts by weight of iodine, per million parts of polycaprolactam. Composition (1) contains no stabilizer, composition (2) contains 0.50 g. of iodoform (:96 parts I), composition (3) contains 0.76 g. of copper acetate (:48 parts Cu), composition (4) contains 0.76 g. of copper acetate (:48 parts Cu), 0.50 g. of iodoform (:96 parts I), and 15 g. of titanium dioxide (:0.3%), and composition (5) contains 0.76 g. of copper acetate (:48 parts Cu), 0.74 g. of iodo-cyclopentane (:96 parts J), and 15 g. of titanium oxide (:0.3%).

From each composition yarns are melt-spun and colddrawn, each yarn having a total of 70 denier (:8 tex) and comprising 23 filaments. Each yarn is examined as to: (a) color, reduced viscosity, and tensile strength, when untreated, (b) reduced viscosity and tensile strength, after having been heated in air during 8 hours at 177 C., and (c) tensile strength after having been irradiated during 220 hours in a fadeometer. Ten tests each are made of each yarn according to (a), (b), and (c), and Table I shows the averages of these tests indieating (a) the color, reduced viscosity, and strength of the untreated yarns, (b) the changes of viscosity and strength of the heated yarns expressed in percent of the viscosity and strength of the untreated yarns, and (c) the change of strength of the irradiated yarns expressed in percent of the strength of the untreated yarns.

TABLE I (c) Yarns irradiated (b) Yarns heated 220 hrs. in (a) Untreated yarns 8 hours to 177 C. iadeometer Reduced Change 0t viscosity Tensile 1n 1; rel strength Reduced Tensile Tensile grams viscosity} strength, strength, Stabilizer used Colour 0.2 per denier percent percent percent (1) Colourless.. 1. 14 5. 2 57 53 47 (2) Iodoform Colourl ss 1. 1G 6. 0 -53 --49 -47 (3) Copper acetate 1. 22 5. 5 10 13 26 (4) Copper acetate plus iodolerrn 1.03 4. S) +2 +2 16 (5) Copper acetate plus iodo-cyclopentane. 1. 20 5. 8 +2 2 17 1 Against untreated yarns.

EXAMPLE II Five concentrate polycaprolactam compositions are prepared as described above, each made from 5 kg. of

6 untreated yarns, and (c) the change of strength of the irradiated yarns expressed in percent of the strength of the untreated yarns.

TABLE II (o) Yarns irradiated (b) Yarns heated 220 hrs. in

(a) Untreated yarns 8 hours to 177 C. iadeometer Mixing propor- Reduced Change of tion concenviscosity, Tensile trate/basic 1n n rel strength, Reduced Tensile Tensile polycaprolacgrams per vlscosity, strength, strength, Stabilizer used tam Colour 0.2 denier percent percent percent (7) Copper acetate 1: Pink 1. 22 4. 8 22 26 31 (8) Copper iodide 1:10 Light-violet--- 1 24 5. 6 5 4 16 (9) Copper iodide plus iodoform. 1:10 Whlte 1. 21 4. 4 +1 +2 (10) Copper acetate plus icdo- 1:10 Colourless. 1. 22 6. 0 +3 4 17 cyclopentane.

(11) Copper iodide plus iodoiorm 1:100 White 1. 24 5. 3 +2 +2 -16 1 Against untreated yarns.

caprolactam, but with dilferent additions, the term parts Cu meaning parts by weight of copper, and the term parts J meaning parts by weight of iodine, per million parts of polycaprolactam. Composition (7) contains 7.55 g. of copper acetate (:480 parts (Cu) composition (8) contains 7.20 g. of copper iodide (:480 parts Cu and 960 parts J) and 150 g. of titanium dioxide (=3.0%), composition (9) contains 7.20 g. of copper iodide, 5.40 g. of iodoform (:480 parts Cu and 2000 parts I), and 150 g. of titanium dioxide (=3.0%), composition (10) contains 7.55 g. of copper acetate and 7.40 g. of iodo-cyclopentane (:480 parts Cu and 960 parts J), and composition (11) contains 72 g. of copper iodide, 54 g. of iodoform (=4800 parts Cu and 20,000 parts J) and 150 g. of titanium dioxide (=3.0%). Composition (7) is red, and compositions (8) to (11) are yellow to brown.

The concentrate compositions (7) to (11) are mixed with a basic polycaprolactam containing no stabilizers or other additions except 0.1 percent of benzoic acid as chain terminator, 5 kg. each of compositions (7 to (10) being mixed with 50 kg. each of basic polycaprolactam, and 5 kg. of composition (11) being mixed with 500 kg. of basic polycaprolactam. From each of the five mixtures yarns are melt-spun and cold-drawn, each yarn having a total of 70 denie'r (=8 tex) and comprising 23 filaments. Each yarn is examined as to: (a) color, reduced viscosity, and tensile strength, when untreated, (b) reduced viscosity and tensile strength, after having been heated in air during 8 hours at 177 C., and (c) tensile strength, after having been irradiated during 220 hours in a fadeometer. Ten tests each are made of each yarn according to (a), (b), and (c), and Table II shows the averages of these tests indicating (a) the color, reduced viscosity, and tensile strength of the untreated yarns, (b) the changes of viscosity and strength of the heated yarns expressed in percent of the viscosity and strength of the The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

I claim:

1. A poly(w-amino carboxylic acid) composition which is stabilized against degradation by heat and light comprising a poly(w-amino carboxylic acid), and from 20 to 5000 parts by weight of copper, derived from a coppercontaining compound selected from the group consisting of copper acetate and copper iodide, and from 50 to 20,000 parts by weight of iodine derived from iodoform per million parts by weight of the poly (to-amino carboxylic acid).

2. A composition in accordance with claim 1 in which the poly(w-amino carboxylic acid) is polycaprolactam.

3. A composition in accordance with claim 1 in which the poly(w-amino carboxylic acid) is poly(w-amino undecanoic acid).

4. A polycaprolactam composition having incorporated therein stabilizing amounts of copper acetate and iodoform.

DONALD E. CZAI A, Primary Examiner V. P. HOKE, Assistant Examiner US. Cl. X.R. 260-457, 78 

